Lung cancer is the leading cause of cancer related deaths in the United States. Despite the identification of several preventive agents and strategies, optimal prevention of lung cancer has not been achieved. More effective agents are therefore required that would safely achieve prevention without drastic side effects.Novel compounds which are rational modifications of well-established chemopreventive agents and follow a similar mechanism of action, but with enhanced potency, reduced toxicity, and lower dose requirement, may be clinically more relevant. Recently, we developed highly innovative hybrid molecules, p-XS-Asp and p-XS-Ibu, designed by conjugating two well known chemopreventive agents i.e. 1,4-phenylenebis(methylene)seleno- cyanate (p-XSC) and nonsteroidal anti-inflammatory drugs (NSAIDs) aspirin and ibuprofen, respectively, as potential agents for lung cancer prevention. The advantage of these agents is two-fold: (i) the combined p- XSC-NSAID hybrid drugs would generate the active p-XSeH putative metabolite similar to p-XSC but without the toxicity related to hydrogen cyanide (HCN); HCN is released as a side product on p-XSC metabolism but would not form in p-XS-NSAID metabolism, and (ii) the novel agents would function through releasing the corresponding NSAID, thus enhancing the overall chemopreventive efficacy of the hybrid molecule. Our preliminary studies supported this assumption and identified p-XS-Asp as the most potent and orally bioavailable agent. The overall goal of this project is to validate the potential of p-XS-Asp as a lung cancer chemopreventive agent. We hypothesize that p-XS-Asp would cleave in vivo to release the active p-XSeH, not releasing undesired HCN but aspirin, thus making it less toxic and more potent than p-XSC or aspirin alone. The objective of this proposal is to test the efficacy of p-XS-Asp for inhibiting lung tumor development using the A/J mouse lung cancer model and to begin evaluating the mechanism by which this agent exhibits its activity. The specific aims are: 1) evaluate the chemopreventive efficacy of p-XS-Asp in NNK-induced lung cancer, and 2) evaluate the mechanism of action(s) associated with chemopreventive effects of p-XS-Asp in NNK-induced tumorigenesis. We will use the experimental approach of determining the maximum tolerated dose (MTD) of dietary p-XS-Asp and evaluating its effectiveness for inhibiting tumor development in A/J mice injected intraperitonealy with one dose of 10 mol NNK in saline. Furthermore, to begin establishing the mechanism, we will carry out its metabolism using liver microsomes to establish if p-XS-Asp will cleave into active metabolites p-XSeH and aspirin, and evaluate COX-2-mediated pro-mitogenic MAPK and pro-survival PI3K/AKT signaling pathways, which are known to be influenced by p-XSC and/or aspirin. These studies will begin establishing the potential of p-XS-Asp as lung cancer preventive agent. Long term, validation of p-XS- Asp as an effective and safe agent would reduce the chances of developing lung cancer, particularly, in smokers/former smokers thereby directly decreasing the mortality incidence. PUBLIC HEALTH RELEVANCE: To date, there are no effective agents available for the prevention of lung cancer which, in ~90% of the cases, is attributed to tobacco use. The studies proposed here, will initiate validation of our recently developed hybrid agent p-XS-Asp as a potent and safe chemopreventive against NNK induced carcinogenesis and begin elucidating underlying mechanism of chemoprevention. If effective,this study would reveal a promising agent which, in near future, could prove capable of preventing lung cancer development in smokers.